Gasket



y 1949; D. D. PERRY 2,469,474

Filed Nov. 8, 11944 VENTOR,

WM a W Patented May 10, 1949 GASKET Daniel D. Perry, Bainbridge, N. Y., assignor to Bendix Aviation Corporation,

New York, N. Y.,

a corporation of Delaware Application November 8, 1944, Serial No. 562,511

5 Claims. 1

,This invention relates to gaskets and more particularly to materials especially adapted for use in sealing joints between connected parts of radio shielding housings or the like.

It has long been standard practice to enclose electrical devices or circuits such as an ignition system of an internal combustion engine in a suitable metallic casing which is electrically grounded for the purpose of preventing electrical and magnetic emanations from said devices or circuits from interfering with radio reception in the vicinity of said engines, such as on aircraft, automobiles, and the like. Much difficulty has been experienced in providing satisfactory, moisture-tight joints between parts of the shielded housings and at the same time insure satisfactory electrical continuity between the parts of the housing which is necessary to accomplish satisfactory elimination of radio interference. This difficulty is greatly enhanced as the frequency of the radio, waves involved increases. Much time and effort has been expended by those skilled in the art in endeavoring to eliminate this shielding diificulty.

It is accordingly an object of the present invention to provide a novelly constructed gasket material which will function as an electrically conductive link between two metallic or other electrically conductive surfaces and at the same time function in a satisfactory manner as sealing means to substantially prevent the passage ofair and moisture between said surfaces.

Another object of the invention is to provide novel apparatus whereby a fluid-tight electrically conductive joint may be formed between two metallic or other electrically conductive parts.

A further object is to provide a novel material for forming gaskets of the above character which may be readily and inexpensively manufactured in large quantities and which may be easily stored and transported.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention, reference for this latter purpose being bad primarily to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

' Fig. 1 is a side elevation, partly in section and with parts broken away, showing one form of gasket material embodying the present invention; and

Fig. 2 is a sectional view, with parts broken away, showing the gasket material of Fig. 1 installed in a novel manner between connected metallic parts.

The single embodiment of the invention illustrated in the drawings, by way of example, comprises a core 5 which may be of any suitable flexible material. Said core is preferably substantially non-yieldable in a radial direction and may be constituted by a wire made of malleablematerial such as copper, for example. Although core 5 may be stranded, it is preferably formed of a single solid wire which is transversely rigid so as to form a firm foundation for the covering or surrounding material to be hereinafter described. In order that the material may be bent into desired shapes and contours and remain so, core 5 is preferably bendable but substantially non-resilient. It is desirable that the ability of the core to remain in a given contour is sufficient to resist the resiliency of the covering or surrounding material. Permanence of length of a gasket for a given installation is desirable for providing a given fit and for avoiding changes of transverse dimensions due to elongation. Accordingly, a core of material which is non-stretchable under ordinary handling and operating conditions is preferable.

For the purpose of rendering the article or material comprehended by the present invention adaptable for use as a gasket in sealing a joint between adjacent surfaces, core 5 is closely surrounded by a covering 6 of material which will flow under pressure, such as comparatively soft natural or synthetic rubber or rubber-like material. When the gasket is intended for use on an internal combustion engine, for example, the covering is preferably constituted by an oil resistant, resilient or yieldable material which is capable of withstanding relatively high temperatures as well as wide and rapid temperature changes. A synthetic elastomer such as neoprene and similar synthetic products have been found to be satisfactory. Covering 6 may be applied to core 5 in accordance with any of several well known processes, such as by extrusion, molding, dipping, or the like. Prior to installation, the external surface of the covering may be cylindrical as shown in Fig. 1 or the same may be of any other suitable shape depending upon the parts in connection with which it is to be used. In some installations it may be desirable to eliminate core 3 l, in which event the yieldable material l may be either solid or tubular.

In order that a satisfactory electrical connection may be assured between parts of a radio shielding housing, for example, the covering and core 5, if one is used, have an electrically conductive wire 1 spirally wound thereon. The size of this wire is very small in comparison to the size of covering 6 and is wound on the latter in the form of a loose or open spiral having a pitch somewhat greater than the diameter of the wire. It has been found desirable, although not strictly necessary, that wire 1 be partially or even substantially embedded in the surface of covering 6 so that only a portion of the wire protrudes outwardly beyond the surface of the covering. By exerting sufficient pressure when winding wire I on covering 6, which is yieldable and internally supported by the transversely rigid core 5, said wire may be initially embeddedin the covering to any desired extent. As pointed out above, the embedding of the wire is not essential but reduces the required flow of the material constituting cover 6 when the gasket is installed in the manner hereinafter described.

In order that a gasket of the above character may present a relatively continuous surface to the surfaces of a joint and thereby satisfactorily seal the joint against the passage of undue quantities of air and moisture, novel means are provided for insuring the filling of the spaces between successive turns of wire I when pressure is applied to the gasket material. In the form shown, said means comprises a strand 8 spirally wound on cover 6 between the successive turns of wire 1. Strand 8 is preferably made of fibrous material such as cotton, linen, or the like. This strand is transversely yieldable under pressure and will supplement the material 6 which flows between successive turns of wire 'I under pressure in completely filling said spaces without interrupting contact between the periphery of the wire and the adjacent surfaces of the joint. Although only one fabric strand 8 is shown, it will be understood that any desired number of such strands may be employed. In installations where it is especially desirable to prevent the passage of moisture through a joint, strands 8 may be treated in any of many well known manners, such as by waxing or oil treating, for example, to render the same substantially moisture repellant and non-absorbent. The pitch of the spiral formed with wire 1 and strand 8 is shown to be relatively small in the drawings, but it will be understood that any suitable pitch may be adopted for any particular installation. As a general rule, the pitch of the spiral windings will varysomewhat with the diameter of the gasket and the flowability of the material 6. The pitch should be sufficiently great to permit flow of the material of coverin 6 into the space between the turns of wire I when pressure is applied during installation in a joint. If desired, the strand or strands 8 may be formed of other suitable yieldable materials such as natural or synthetic rubber or other rubber-like substances. If the fabric or rubber strands 8 predominate overthe wire strands 1, better sealing characteristics will be assured, whereas, for best radio shielding characteristics, the pitch of the spiral formed by wire I may be decreased so that more metal to metal contact between the surface of the joint and the gasket will be obtained. By using a suitable number of strands l of suitable diameter the material of said strands maybe caused under 4 pressure to completely an the space between adjacent turns of wire 1 without depending upon the flowability of the material 'of covering I, in which event said covering together with'core I may be of a rigid nature.

In one embodiment of the invention which has proved practical and successful, both from the standpoint of radio shielding and of sealing a joint against leakage under a differential pressure of more than 5 pounds, core I is made of No. 18 copper wire having a diameter of about .04 inch and covering 6 is made of neoprene." the outside diameter of the latter being approximately .110 inch. To make the gasket particularly suitable between magnesium alloy parts of a shielding casing, such as are currently used in the ignition systems of aircraft engines, wire 1 is made of aluminum alloy having a diameter of approximately .008 inch and is spirally wound on the core structure 5, 6 at the rate of about thirty turns to-the inch. wire 1 should have a low corrosion factor with respect to the metal which it is intended to engage so that galvanic action and, hence, corrosion, will be reduced to a minimum. For reasons which will more fully appear hereinafter, it is desirable in some installations to employ sturdy or stiff spring wire in forming the turns 1. The size of thread or strand 8 will, as pointed out above, depend upon the size of wire 1, the pitch of the turns of wire I, and the flowability of the material 6 under pressure.

In Fig. 2 of the drawings the above-described gasket forming material is illustrated in novel combination with two parts which are connected together to form a joint. The joined metallic parts 9 and 10 may be considered to represent parts of a radio shielding harness, the casing of a magneto generator or the like, the same being joined together by any suitable means such as bolts H. The gasket is preferably placed in a novelly formed groove [2 in one of the connected parts, such as part l0, and if desired said gasket may be cemented or adhesively secured in said groove for the purpose of avoiding unnecessary or accidental removal thereof when the parts 9 and in are disconnected. For this purpose, an oil modified alkyd resin reaction product has been found suitable although there are many similar products having adhesive properties which will give satisfactory results. The resinous material may be dissloved in a solvent such as melamine formaldehyde to form a tacky liquid for application to the walls of groove ll. After the solvent has evaporated from the coating on said walls, a deformable adhesive him will remain-a film which is fiowable under relatively low pressure. The gasket may then be inserted into the groove and sufficient pressure applied to the same to cause the turns of wire 1 to cut through the flowable adhesive film and make good electrical contact with the walls of the groove. The adhesive film may then be set by the application of heat to form a tough, non-brittle film without appreciable shrinkage. In addition to retaining the gasket within the groove the adhesive film also cooperates with the same to provide fluid tightness between the gasket and the surfaces of the groove, 1. e., between the gasket and part in. i

The relative sizes of groove II and the gasket material are such that the latter projects slightly from the groove so that the same will make good contact with the surface I of part 9. Accordingly, when part I is secured in position on part iii, the surface ll of the former first engages the turns of wire I. When pressure is applied through the medium of bolts H, the turns of wire I tend to flatten out at the points where pressure is applied so as to present a greater surface of contact to the surface ID, for example. The application of pressure also causes the material of covering 6 to be deformed and to flow into the space between successive turns of wire 1. This also results in a suitable deformation of the strand or strands 8 to complete the filling of said'spaces and, hence, causes corresponding portions of turns 1 and 8 to present a relatively wide, fiat, continuous surface to surface ll of member 9. A satisfactory seal against moisture as well as a satisfactory electrical connection between parts 9 and 10 may thus be accomplished.

In order to better accommodate the gasket in groove [2 when the same is deformed under pressure and to avoid the formation of sharp bends in wire] when parts 9 and ID are clamped together, the upper corners of said groove are preferably beveled, as shown at 13. The beveling of these corners also permits the gasket to deform in such a manner as to present a wider surface for engagement by the surface H of part 9. Th inclination of the bevel and the extent thereof will depend somewhat upon the size of the groove and the gasket and upon the portion of the gasket which extends out of the groove when the same is initially installed. In some installations, it

may be desirable, as shown in the left half of Fig. 2, to have the surface l5 around the inner periphery of groove I2 in a different plane from the surface i6 surrounding said groove so that metal to metal surface contact may be obtained between surfaces [4 and I6 while sufilcient pressure is also applied to the gasket to render it operative for its intended purposes.

There is thus provided a novel product or article of manufacture which may be employed in a novel manner in sealing a Joint between surfaces of connected parts to prevent the leakage of air and moisture and at the same time to function as means for electrically connecting said parts to thereby insure good radio shielding characteristics. Additionally, the gasket material provided by the present invention is constructed in a novel manner so that it may be easily bent and cut to the desired lengths for particular installations. Said material may be readily and quickly manufactured in large quantities at low cost and may be transported and stored for easy installation in structures of various sizes and shapes in the field.

Although only a single embodiment of the invention is illustrated and described in detail, it is to be expressly understood that the same is not limited thereto. For example, the various materials mentioned as being suitable or preferable for the several parts of the gasket structure may be replaced by other materials having similar properties. Various other changes may also be made, such as in the size, shape and arrangement of parts illustrated. without departing from the spirit and scope of the invention as will now be readily apparent to those skilled in the art. For a definition of the limits of the invention, reference is had primarily to the appended claims.

What isclaimed is:

1. An electrically conductive gasket comprising an elongated core including a strip of metal and a covering of yieldable rubber-like material closely surrounding said strip, a metallic wire round in cross-section wound on said covering in the form of an open spiral, the turns of said wire being spaced from each other and partially embedded in the surface of said covering, and a thread of fibrous material wound on said covering in the form of an open spiral and directly contacting said covering, the turns of said thread being wholly disposed between the turns of said wire in non-lapping relation.

2. In apparatus of the class described, two metallic parts having adjacent surfaces, at least one of said surfaces having a groove therein with at least one of the outer corners thereof beveled, a gasket substantially filling said groove and protruding therefrom, said gasket comprising a transversely yieldable core, a wire and a thread of yieldable material, said wire and thread being spirally wound on said core, and means for clamping said parts together with the other of said surfaces pressing against the protruding portion of said gasket.

3. In apparatus of the class described, two metallic parts having adjacent surfaces, at least one of said surfaces having a groove therein and at least one of the outer corners of said groove being beveled, a gasket substantially filling said groove and protruding therefrom, said gasket comprising a transversely yieldable core and a strand of electrically conductive material wound on said core in the form of an open spiral, and means for clamping said parts together with the other of said surfaces pressing against the protruding portion of said gasket sufficiently to cause the latter to be deformed and extend into the space formed by said beveled corner.

4. A gasket adapted for use between radio shieldin parts comprising a metallic wire round in cross-section and ,a strand of transversely yieldable material round in cross-section spirally wound in non-lapping relation around an elongated body of yieldable material, the turns of said wire and strand being alternately arranged and having continuous contact throughout their lengths with the surface of said body.

5. A gasket adapted for use between radio shielding parts comprising at least one strip of electrically conductive material round in crosssection and at least one strand of fibrous material spirally wound in non-lapping relation with said strip around an elongated core of transversely yieldable flexible material, the turns of said strip and strand being alternately arranged and having continuous contact throughout their lengths with the surface of said core.

DANIEL D. PERRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain June 21, 1938 

